Season tuna with salt and pepper. Roll in sesame seed and pat seeds to tuna . Put grape seed oil in cast iron pan and heat to a high temp, add tuna, cook for 2 minutes on each side and ends. Turn off heat and let tuna sit in pan for 2-3 minutes.
Serve with wasabi sauce. Mix Cream or mayo with wasabi add fish sauce, maple syrup, sambal and soy sauce.